Among the stable oxygen isotopes 160, 17O and 18O, 17O is the only one that has nuclear spin. For this reason, compounds labeled with 17O have been used for research purposes such as structural analysis by means of nuclear magnetic resonance, and used as a tracer in such fields as chemistry and medicine. They are also considered useful in medicine as the material to manufacture the diagnostic agent 18FDG (PET contrast medium made by labeling fluorodeoxyglucose with a fluorine 18 radioactive isotope having a positron-emitting nuclide) used in positron emission tomography diagnosis (PET) of tumors and other anomalies.
While 17O and 18O are useful isotopes for industrial purposes, they exist in extremely low abundance in nature. Therefore, in order to use the isotope in practical application, 17O and/or 18O must be concentrated from compounds that include oxygen atoms.
As the conventional method for concentrating 17O, for example, the following conventional methods have been known.
There is a method of distilling water as the starting material so as to concentrate 17O up to 25 atom %, and then concentrating it to 90 atom % by thermal diffusion (Non-Patent Document 1). Another method uses nitrogen monoxide (NO) as the starting material and distils it to concentrate 17O, and then uses thermal diffusion to concentrate 17O to a high concentration (for example, 40 atom %) (Non-Patent Document 4). Another method uses oxygen as the starting material and distills it to concentrate 17O to 10 atom % (Patent Document 1). Another method employs photopredissociation of formaldehyde by means of irradiation with a Ne ion laser so as to concentrate 17O (Non-Patent Document 2, Patent Documents 5 and 6). There are also such methods as ozone is irradiated with visible light and ultraviolet rays (Non-Patent Document 3) and a semiconductor laser is used to separate ozone molecules that include 17O by photodissociation, thereby to enrich 17O in oxygen (Non-Patent Documents 2, 3 and 4).    [Patent Document 1] International Publication No. WO00/27509    [Patent Document 2] Japanese Unexamined Patent Application, First Publication No. 2004-261776    [Patent Document 3] Japanese Unexamined Patent Application, First Publication No. 2005-040668    [Patent Document 4] International Publication No. WO2004/078325    [Patent Document 5] U.S. Pat. No. 4,029,559    [Patent Document 6] U.S. Pat. No. 4,029,558    [Non-Patent Document 1] I. Dostrovsky: “The production of stable isotope of oxygen”, Analytical Chemistry Symposium Series pp. 693-702 (1982)    [Non-Patent Document 2] Jack Marling: “Isotope separation of oxygen-17, oxygen-18, carbon-13 and deuterium by ion laser induced formaldehyde photopredissociation”, The Journal of Chemical Physics, Vol. 66, No. 9, pp. 4200-4225 (1977)    [Non-Patent Document 3] J. Wen and Mark H. Thiemens: “Experimental and theoretical study of isotope effects on ozone decomposition”, J. Geophysical Research, Vol. 96, No. D6, pp. 10911-10921 (1991)    [Non-Patent Document 4] McInteer, B. B.; Potter, Robert M.: “Nitric oxide distillation plant for isotope separation”, Ind. Eng. Chem., Process Design Develop., 4(1), 35-42 (1965)